Research Journal of Environmental and Earth Sciences 4(1): 99-104, 2012
ISSN:
©Maxwell Scientific Organization, 2012
Submitted: August 11, 2011
Accepted: September 25, 2011
Published: January 01, 2012
Radiochemical Pollutants Concentration in Ghanaian Cement by Instrumental
Neutron Activation Analysis and (-Ray Spectrometry
1
D.O. Kpeglo, 1H. Lawluvi, 1A. Faanu, 1A.R. Awudu, 1C.C. Arwui, 1P. Deatanyah,
S. Wotorchi-Gordon, 1,3E.O. Darko, 1,3G. Emi-Reynolds, 2N.S. Opata and 2I.K. Baidoo
1
Radiation Protection Institute,
2
National Nuclear Research Institute, Ghana Atomic Energy Commission,
P.O. Box LG80, Legon-Accra, Ghana
3
Graduate School of Nuclear and Allied Sciences, University of Ghana, Atomic-Campus,
P.O. Box AE1, Atomic Energy, Ghana
1
Abstract: Instrumental Neutron Activation Analysis (INAA) has been used to identify and quantify
concentrations of eighteen major, minor and trace elements (Ca, Fe, Al, Sc, Na, K, Ti, Mn, Cr, Zn, Co, As, Cd,
Hg, V, La, U and Th) in five different brands of Ghanaian cement samples used in the building and construction
industry. The (- spectrometric and INAA techniques used for the determination of U, Th, and K complemented
each other very well in this study. Generally, concentrations of toxic elements determined in the five brands
were low. However, the continuous inhalation or ingestion by occupational staff makes the smallest
concentration of these toxic elements a potential risk to their health.
Key words: Major elements, minor elements, portland cement, risk, trace elements, white cement
INTRODUCTION
Rigorous infrastructural development is a common
phenomenon in a developing country like Ghana. The
activities of this sector results in the pollution of the
environment and subsequent inhalation of dust containing
metal pollutants which may pose serious health risk to
persons working directly within this industry and the
entire population at large.
Environmental contamination by many pollutants is
one of the most serious problems in this century. Cement
one of the most important materials in the construction
industry may be a source of large amounts of dust
polluting the air with heavy metals which are more or
less, toxic to humans and animals. Cement dust spreads
along a large area through wind, rain, etc., and are
accumulated in and on plants, animals, and soil and can
have very negative effects on human health (Ayvaz, 1992;
Is2kl2 et al., 2003).
Portland cement dust may be a source of
environmental pollutants with a well defined toxic
pathology. Especially known are the toxic effects of
arsenic, cadmium, lead, mercury and thallium (Domingo,
1994; Chang, 1996). Aluminium, berillium, chromium,
copper, manganese, nickel, and zinc, among others, have
been also identified in theemissions from cement plants.
While some of these elements are essential for humans, at
high levels they can also mean a toxicological risk
(Domingo, 1994; Chang, 1996).
Portland cement dust is a gray powder with an
aerodynamic diameter ranging from 0.05 to 5.0 :m
(Kalacic, 1973a). This size is within the range of sizes of
respirable particles, and, therefore, exposure to Portland
cement dust has long been associated with respiratory
symptoms and varying degrees of airway obstruction in
people who work with Portland cement (Bazas, 1980; ElSewefy et al., 1970; Kalacic, 1973a, b; Noor et al., 2000;
Oleru, 1984; Saric et al., 1976; Shamssain et al., 1988;
Yang et al., 1996)
Various analytical techniques have been used in the
elemental analysis of Portland cement. Common among
them are Wet Chemical Analysis, Radioisotope x-ray
fluorescence analysis, Atomic Absorption, XRF,WDXRF,
EDXRF, and INAA (Kristmann, 1977; Sarkar, 1978;
Muhyedeen et al., 2001).
INAA is a powerful analytical technique that is based
on nuclear reactions and capable of detecting many
elements at extremely low concentration. INAA is cost
effective and affordable for small and large sample
quantities and offers superior sensitivity to many elements.
It is essential to know the elemental content of
materials producing dust as this is an important
determinant of air quality because of the potential toxicity
of these metal pollutants to humans and the environment.
The aim of the study therefore was to determine the
major, minor and trace elemental concentrations of cement
samples used in Ghana and to compare the concentrations
Corresponding Author: D.O. Kpeglo, Radiation Protection Institute, Ghana Atomic Energy Commission, P.O. Box LG80, LegonAccra, Ghana
99
Res. J. Environ. Earth Sci., 4(1): 99-104, 2012
of U, Th and K determination using instrumental neutron
activation analysis and gamma spectrometry.
system) at a pressure of 0.6 Mpa. At the inner
pneumatic(GHARR-1) facility. GHARR-1 is a 30KW
tank-in-pool irradiation sites, the samples are irradiated
with a thermal flux of 5×1011 nc/m2s when the reactor
operated at half full power of 15 Kw. Irradiation times
ranged from 10 s to 1 h according to the half-lives of the
elements of interest. For elements with relatively short
half-lives such as Ca, Al, Mn, Ti, and V, with half-lives
between 2 minand 15 h, irradiation time was 10 s and
counting time was 10 min. The samples were analyzed
using irradiation schemes by optimizing irradiation time
(ti), decay time (td) and counting time (tc) based on the t1/2
of respective elements. After the irradiation, radioactivity
measurement of induced radionuclides was performed by
a PC-based (-ray spectrometry set-up. It consisted of an
n-type high purity germanium (HPGe) detector Model GR
2518 (Canberra Industries Inc.) coupled to a computer
based PCA-MR 8192 Multi-channel Analyzer (MCA)
mounted in a cylindrical lead shield (100 mm thick) and
cooled in liquid nitrogen with a resolution of 1.8 KeV
(FWHM) for 60Co gamma-ray energies of 1332 KeV and
a peak-to-Compton ratio of 55:1. The detector operated on
a bias voltage of -3000V with relative efficiency of 25%
to NaI detector. A Microsoft Soft window based software
ORTEC MAESTRO-32 was used for the spectrum
analysis. The analytical photopeaks used for the
determination of the various elements have been
summarized in Table 1.
Validation of the technique for the experimental setup
was carried out by irradiating a standard reference
material (IAEA Soil -7) for the same period of time as the
samples, with comparator and the sample in the same
location within the reactor. The analysis of the standard
reference materials in Table 2 shows good agreement of
measured values with the certified ones.
MATERIALS AND METHODS
The study was carried out at the Ghana Research
Reactor -1 Centre (GHAAR-1) and Radiation and waste
safety Department of the Radiation Protection institute,
Ghana Atomic Energy Commission from April, 2010 to
December, 2010.
Sampling and sample preparation: Five different
brands of cement samples manufactured and used in the
construction industry of Ghana were collected from
different cement suppliers for the measurement of
elemental concentrations. The cement samples were used
without any processing since they are already in a
powdered form. The samples were dried in a temperaturecontrolled furnace at 110ºC for 24 h to remove moisture.
After moisture removal, these samples were cooled in
moisture-free atmosphere and pulverized into fine
powdered form. Three replicate samples, about 100 mg
each, were weighed and sealed into polythene bags. Equal
weights of GBW07106 and IAEA Soil 7 reference
materials were also weighed and sealed into polythene
bags for the quantitative analysis of the elements in the
cement samples and validation of the analytical tool,
respectively. The sealed bags were then packed into
plastic rabbit capsules labeled by a marker, and heat
sealed using a soldering iron.
Irradiation and counting: Samples and standard
reference materials were irradiated in the inner pneumatic
irradiation sites of the Ghana Research Reactor-1 reactor
using light water as moderator and coolant. The fuel
source is highly enriched Uranium (90.2%-Al alloy) with
metal beryllium as reflectors. The reactor is cooled by
natural convection. Samples were transferred into
irradiation sites via pneumatic transfer system (rabbit
Calculation of metal concentrations in samples:
Collision of thermal neutrons with a nucleus during
irradiation of a sample may result in a number of
reactions and useful among these reactions in NAA is
Table 1: Nuclear data of elements used in analysis
Element
Radioisotope
Energy (keV)
51
Titanium (Ti)
Ti
320.1
52
Vanadium (V)
V
1434.1
60
Cobalt (Co)
Co
1332.2
51
Chromium (Cr)
Cr
320.0
59
Iron(Fe)
Fe
1098.6
140
Lanthanum (La)
La
328.8
1596.2
28
Aluminium (Al)
Al
1778.9
56
Manganese (Mn)
Mn
1810.7
46
Scandium (Sc)
Sc
889.3
1120.5
42
Potassium (K)
K1
1524.7
239
Uranium (U)
Np
277.7
233
Thorium (Th)
Pa
311.9
65
Zinc (Zn)
Zn
1115.5
197
Mercury (Hg)
Hg
77.4
115m
Cadmium (Cd)
In
336.3
76
Arsenic (As)
As
559.1
49 Ca
Calcium
3084.4
100
Half-life
5.8 min
3.76 min
5.2 7y
27.72 y
44.5 d
44.5 d
40.23 h
2.24 min
2.58 h
83.8 d
Irradiation time
10 s
10 s
1h
1h
1h
1h
Counting time
10 min
10 min
2h
2h
2h
10 s
10 s
1h
2h
10 min
10 min
2h
12.36 h
2.35 d
27.0 d
243.8 d
64.1 h
53.5 h
26.3 h
8.7 min
1h
1h
1h
1h
1h
1h
1h
10 s
2h
2h
2h
2h
2h
2h
2h
10 min
Res. J. Environ. Earth Sci., 4(1): 99-104, 2012
Table 2: Analysis of standard reference material by INAA (IAEASOIL-7) (in mg/kg)
Element
Measured value
Certified value
Ti
3002
3000
V
66
66
Co
8.8
8.9
Cr
59.2
60
Fe
25701
25700
La
27.5
28
Al
4703
4700
Mn
630
631
Sc
8.4
8.3
K
12105
12100
U
2.4
2.6
Th
8.1
8.2
Zn
102
104
Hg
0.03
0.04
Cd
1.2
1.3
As
13.2
13.4
Ca
162998
163000
where, Csam is the unknown concentration of the element
in the sample, Cstd is the known concentration of the
element in the standard, Asam is the activity of the sample
and Astd is the activity of the standard.
Comparison of instrumental neutron activation
analysis and Gamma ray spectrometry: The
concentration of U, Th, and K where determined by
INAA while radioactive 238U, 232Th, and 40K was also
determined by gamma ray spectrometry and have already
been reported in our previous study (Kpeglo et al., 2011),
and are shown in Table 4. Considering the fact that these
primordial radionuclides (238U, 232Th and 40K) exhibits a
constant atomic abundance in nature, it is possible to
convert the specific activities of 238U, 232Th, and 40K into
massic elemental concentrations of U, Th, and K
respectively in order to compare the two techniques using
the following formula:
radiative capture which can be represented by the
equation (Landsberger, 1994).
n + AZ ÷ A+1Z* ÷ A+1Z + (
A
CE = (T1/2 . R . Ma . Asp)/(Pa . NA. ln2)
(1)
where, CE is the elemental concentration in sample, Ma is
the atomic mass (kg/mol), T1/2 is the half-life (sec), Pa is
the fractional atomic abundance in nature (%), NA is
Avogadro’s constant (6.023×1023 g/mol), Asp is the
measured activity concentration (Bq/kg) of the
radionuclide considered (238U, 232Th, or 40K), and R is a
constant with a value of 1,000,000 for U and Th
(concentration in :g/g) or 100 for K (concentration in %
of mass fraction).
A+1
where; Z is the target nucleus, Z* is a compound
nucleus in an excited state which de-excites with the
emission of gamma ray called prompt gamma, A+1Z is the
product after irradiating the target nucleus which is
radioactive.
By the comparator method using the same geometry,
equal weights of both sample and standard, with the same
irradiation, decay and counting times, the concentration of
the metals in the samples was determined by the
expression:
Csam = Cstd (Asam/Astd)
(3)
RESULTS AND DISCUSSION
Eighteen Major, minor and trace elements including
U, Th, and K were determined for 5 different brands of
(2)
Table 3: Calculated mean metal concentrations in the different brands of cement samples by INAA
Concentration( :g/g)
-------------------------------------------------------------------------------------------------------------------------------------------------------Elements
CM I
CM I I
CM I I I
CM IV
CMV
Ti
0.26±0.02
0.13±0.01
0.31±0.02
0.24±0.03
0.11±0.01
V
76.32±6.40
54.31±5.10
48.31±4.10
27.48±3.30
24.16±1.30
Al
50193±285
48094±312
41982±209
38568±620
39772±515
Mn
392±53
345±49
238±38
204±29
286±41
Ca
109587±4991
99587±3372
64341±1884
53912±1472
32454±920
La
952±110
697±103
580±46
420±21
610±89
Cd
0.30±0.04
0.23±0.02
0.13±0.01
0.11±0.01
0.15±0.02
As
2.10±0.12
1.60±0.16
1.2±0.07
0.6±0.05
0.3±0.04
Na
4594±121
3881±64264
0±59
1309±19
1889±28
K (%)
2.0±0.1
0.5±0.1
0.6±0.1
0.4±0.1
0.3±0.02
U
3.0±0.2
4.2±0.3
2.7±0.2
2.5±0.3
3.1±0.4
Th
9.1±0.8
6.5±0.6
5.2±0.6
4.3±0.5
5.3±0.6
Sc
34±2.10
28±2.2
40±3.5
24±1.7
30±4.2
Fe
4211±1003
3644±809
2450±542
1830±480
1920±462
Co
27±1.8
34±8.4
10.8±1.3
19.4±1.6
24±2.1
Cr
7.4±1.8
4.1±0.5
6.3±1.7
1.9±0.2
3.5±1.1
Hg
0.12±0.03
0.10±0.02
0.14±0.01
0.20±0.08
0.15±0.04
Zn
18±3.2
12±2.5
9±2.0
10±3.7
4±0.6
*CM I: Portland limestone cement; CM II: Portland limestone cement; CM III: Ordinary Portland cement; CM IV: White cement (Tile adhesive cement
cole); CM V: White cement (Tile adhesive cement)
101
Res. J. Environ. Earth Sci., 4(1): 99-104, 2012
CMIV and Zn from 18 to 4 :g/g for CMI and CMV
respectively. The Hg concentration ranged from 0.10
to 0.20 :g/g. The concentration of Cd ranged from
0.30 :g/g in CMI to 0.11 :g/g in CMIV.
It can also be seen that by comparison the
concentration of the trace elements were lower than that
of the minor and major elements. The concentrations of
the major elements were within the range of the
international standard specification. However, the
variations and low concentration among the minor and
trace elements do not affect the quality.
The variations in the level of trace elements in the
cement products is dependent on both the primary raw
materials (calcium carbonate in the form of chalk or
limestone, and alumina and silica in the form of clay or
shale) and secondary raw materials (Gypsum,
phosphogypsum, pozzolanas, fly ash, blast furnace slag,
iron oxide, and spent catalysts), and fuel (coal, petroleum
coke, used oil, and scrap tires) used in the manufacturing
of particular brand of cement.The levels of trace elements
concentrations in portland cement obtained in this study
compares well with data from other published work
(Muhyedeen et al., 2001; PCA, 1992).
Trace elements are very important for environmental
pollution control because of their potential toxicity. Dust
from the use of cement and subsequent inhalation or
ingestion by occupational staff in the construction
industry is inevitable in developing part of the world and
hence metal toxicants in these cement brands may
constitute potential health risk.
Generally, concentrations of toxic elements
determined in the five brands were low. However,
concerns may be raised on the part of workers who use
these brands of cement for construction and building and
are exposed to the particulate matter almost all day all
their lives. The continuous inhalation or ingestion makes
even the smallest concentration of such toxic elements a
concern to their health.
These are because; the effects of exposure to any
hazardous substance depend on the route of the exposure
(skin, inhalation, and ingestion), how long the exposure
lasts, and how high the exposure is. In any person, the
effects also depend on the person’s health history,
cement samples used in the construction industry of
Ghana. Table 3 presents the average elemental
concentrations in the varieties of cement products using
INAA. The elements determined in all the five brands of
cement samples were Ca, Fe,Al, Sc, Na, K, Ti, Mn, Cr,
Zn, Co, As, Cd, Hg, V, La, U, and Th. From Table 3, it
was observed that, in general concentrations of the
elements in Portland limestone cement were higher than
that found in which (tile adhesive cement).
The analysis of major elements (Fe, Ca, Al) show
that, Ca concentration is very high in all the brands with
CMI registering the highest concentration (109587 :g/g)
and CMV the least concentration (32454 :g/g).
Concentration of Al ranged from 50193 to 38568 :g/g for
CMI and CMIV respectively. Amongst these major
elements Fe recorded lower concentration ranging from
4211 to 1830 :g/g for CMI and CMIV respectively. The
concentration of minor elements such as Na, Ti, Mn also
exhibited a wide variations. Whiles Ti recorded very
small concentrations in the range of 0.11 to 0.31 :g/g for
CMV and CMIII, respectively, concentrations of Mn
varied from 392 :g/g in CMI to 204 :g/g in CMIV. Na on
the other hand recorded concentrations in the range of
4594 to 1309 :g/g for CMI and CMIV respectively.
The concentration ranges of trace elements in the
Ghanaian cement varied from product to product. As
concentration ranged from 0.3 to 2.1 :g/g with CMI
registering the highest concentration and CMV the lowest
compared. A similar order could be said for Cr and Zn
with Cr varying from 7.4 :g/g in CMI to 1.9 :g/g in
Specific activity of 238U, 232Th and 40Kfrom samples of
different brand of Ghanaian cement (Kpeglo et al., 2011)
Mean specific activity (Bq/kg)
---------------------------------------------------------------238
232
40
U
Th
K
Sample ID*
CM I
35±0.8
38±0.9
655±3.5
CM II
51±1.2
27±0.8
124±2.9
CM III
32±0.7
22±1.1
209±6.4
Table 4:
CM IV
28±0.6
18±0.8
99±3.2
CM V
34±0.5
22±0.4
68±1.8
AVE±SD
36±0.8
25±0.8
233±4.0
*CM I: Portland limestone cement; CM II: Portland limestone cement;
CM III: Ordinary Portland cement; CM IV: White cement (Tile adhesive
cement cole); CM V: White cement (Tile adhesive cement)
Table 5: Comparison of elemental concentrations of U, Th, and K in cement samples as determined by instrumental neutron activation analysis and
gamma spectroscopy
Neutron Activation Analysis
Gamma Spectroscopy
----------------------------------------------------------------------------------------------------------------------Th (:g/g)
K (%)
U (:g/g)
Th (:g/g)
K (%)
Sample ID*
U (:g/g)
CMI
3.0±0.2
9.1±0.8
2.0±0.1
3.1±0.1
9.4±0.2
2.1±0.01
CMII
4.2±0.3
6.5±0.6
0.5±0.1
4.4±0.1
6.6±0.2
0.4±0.01
CMIII
2.7±0.2
5.2±0.6
0.6±0.1
2.8±0.1
5.4±0.3
0.7±0.02
CMIV
2.5±0.3
4.3±0.4
0.4±0.1
2.4±0.1
4.4±0.2
0.3±0.01
CMV
3.1±0.4
5.3±0.6
0.3±0.02
3.0±0.04
5.4±0.1
0.2±0.01
AVE±SD
3.1±0.3
6.1±0.6
0.8±0.1
3.1±0.1
6.2±0.2
0.7±0.01
*CM I: Portland limestone cement; CM II: Portland limestone cement; CM III: Ordinary Portland cement; CM IV: White cement (Tile adhesive cement
cole); CM V: White cement (Tile adhesive cement)
102
Res. J. Environ. Earth Sci., 4(1): 99-104, 2012
personal traits and habits, and whether other chemicals are
present. The level of toxicity found may not be problem
in the short term but in the long term it raises concerns.
The mean elemental concentrations of U, The and
K varied in the range of 2.5-4.2 :g/g, 4.3-9.1 :g/g, and
0.3-2.0%, respectively.
In Table 5, the concentration of U, Th and K
determined by INAA and (- spectrometry are compared.
The (- spectrometric analysis results in Bq/kg (Table 4)
were converted to :g/g using Eq. (3). It can be seen that
the two techniques are in very good agreement. The good
correspondence of the primordial radioelement’s
concentrations is an indication of a good equilibrium
between 238U, 232Th and their short-lived daughter nuclides
and also a good calibration and validation of the analytical
techniques.
are exposed to the particulate matter almost all day all
their lives. The continuous inhalation or ingestion makes
even the smallest concentration of such toxic elements a
concern to their health. This is because; the effects of
exposure to any hazardous substance depend on the route
of the exposure, how long the exposure lasts, and how
high the exposure is. In any person, the effects also
depend on the person’s health history, personal traits and
habits, and whether other chemicals are present. The level
of toxicity found may not be problem in the short term but
in the long term it raises concerns.
ACKNOWLEDGMENT
The authors are grateful to cement retail contractors
for their useful contributions in terms of materials and to
the staff of the Ghana Research reactor -1 centre of the
National Nuclear Research Institute, and Radiation and
waste safety Department of the Radiation Protection
institute, Ghana Atomic Energy Commission for their
technical support.
CONCLUSION
The elemental concentrations of eighteen major,
minor, and trace elements as well as U, Th, and K in five
different brands of Ghanaian cement has been
investigated using Instrumental Neutron Activation
Analysis technique. The analytical techniques INAA and
(-spectrometry have also been compared by the
determination of the elemental concentration of U, Th and
K using the two nuclear analytical techniques. The (spectrometric and INAA techniques complemented each
other very well in this study.
The elements determined in all the five brands of
cement samples were Ca, Fe, Al, Sc, Na, K, Ti, Mn, Cr,
Zn, Co, As, Cd, Hg, V, La, U, and Th. It was observed
that, in general concentrations of the elements in Portland
limestone cement were higher than that found in white
(tile adhesive cement).
It can also be seen that by comparison the
concentration of the trace elements were lower than that
of the minor and major elements. The ranges of
concentrations for major and minor elements, which are
responsible for high quality, are in good agreement with
international British standards of specification. The
concentrations of trace elements for this work compared
well with data from other countries.
The variations in the level of trace elements in the
cement products is dependent on both the primary raw
materials (calcium carbonate in the form of chalk or
limestone, and alumina and silica in the form of clay or
shale) and secondary raw materials (Gypsum,
phosphogypsum, pozzolanas, fly ash, blast furnace slag,
iron oxide, and spent catalysts), and fuel (coal, petroleum
coke, used oil, and scrap tires) used in the manufacturing
of particular brand of cement.
Generally, concentrations of toxic elements
determined in the five brands were low. However,
concerns may be raised on the part of workers who use
these brands of cement for construction and building and
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